在Android AMS(二) App启动过程之onCreate中讲到，在activity到onCreate状态前，会调用Activity.java–>attach()方法
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config, String referrer, IVoiceInteractor voiceInteractor,
Window window, ActivityConfigCallback activityConfigCallback) {
attachBaseContext(context);
mFragments.attachHost(null /*parent*/);
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setWindowControllerCallback(this);
mWindow.setCallback(this);
mWindow.setOnWindowDismissedCallback(this);
mWindow.getLayoutInflater().setPrivateFactory(this);
if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
mWindow.setSoftInputMode(info.softInputMode);
}
if (info.uiOptions != 0) {
mWindow.setUiOptions(info.uiOptions);
}
mUiThread = Thread.currentThread();
mMainThread = aThread;
mInstrumentation = instr;
mToken = token;
mIdent = ident;
mApplication = application;
mIntent = intent;
mReferrer = referrer;
mComponent = intent.getComponent();
mActivityInfo = info;
mTitle = title;
mParent = parent;
mEmbeddedID = id;
mLastNonConfigurationInstances = lastNonConfigurationInstances;
if (voiceInteractor != null) {
if (lastNonConfigurationInstances != null) {
mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;
} else {
mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,
Looper.myLooper());
}
}
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
if (mParent != null) {
mWindow.setContainer(mParent.getWindow());
}
mWindowManager = mWindow.getWindowManager();
mCurrentConfig = config;
mWindow.setColorMode(info.colorMode);
}
函数首创建一个类型为PhoneWindow的应用程序窗口，并且保存在Activity类的成员变量mWindow中。有了这个类型为PhoneWindow的应用程序窗口，函数接下来还会调用它的成员函数setWindowControllerCallback、setCallback、setSoftInputMode和setWindowManager来设置窗口回调接口、软键盘输入区域的显示模式和本地窗口管理器。
new PhoneWindow
public class PhoneWindow extends Window implements MenuBuilder.Callback {
......
public PhoneWindow(Context context) {
super(context);
mLayoutInflater = LayoutInflater.from(context);
}
/**
* Constructor for main window of an activity.
*/
public PhoneWindow(Context context, Window preservedWindow,
ActivityConfigCallback activityConfigCallback) {
this(context);
// Only main activity windows use decor context, all the other windows depend on whatever
// context that was given to them.
mUseDecorContext = true;
if (preservedWindow != null) {
mDecor = (DecorView) preservedWindow.getDecorView();
mElevation = preservedWindow.getElevation();
mLoadElevation = false;
mForceDecorInstall = true;
// If we're preserving window, carry over the app token from the preserved
// window, as we'll be skipping the addView in handleResumeActivity(), and
// the token will not be updated as for a new window.
getAttributes().token = preservedWindow.getAttributes().token;
}
// Even though the device doesn't support picture-in-picture mode,
// an user can force using it through developer options.
boolean forceResizable = Settings.Global.getInt(context.getContentResolver(),
DEVELOPMENT_FORCE_RESIZABLE_ACTIVITIES, 0) != 0;
mSupportsPictureInPicture = forceResizable || context.getPackageManager().hasSystemFeature(
PackageManager.FEATURE_PICTURE_IN_PICTURE);
mActivityConfigCallback = activityConfigCallback;
}
......
}调用LayoutInflater的静态成员函数from创建一个LayoutInflater实例，并且保存在成员变量mLayoutInflater中，这样，PhoneWindow类以后就可以通过成员变量mLayoutInflater来创建应用程序窗口的视图
Window.setCallback
public abstract class Window {
......
private Callback mCallback;
......
/**
* Set the Callback interface for this window, used to intercept key
* events and other dynamic operations in the window.
*
* @param callback The desired Callback interface.
*/
public void setCallback(Callback callback) {
mCallback = callback;
}
......
}我们看下这个Callback接口
public interface Callback {
public boolean dispatchKeyEvent(KeyEvent event);
public boolean dispatchKeyShortcutEvent(KeyEvent event);
public boolean dispatchTouchEvent(MotionEvent event);
public boolean dispatchTrackballEvent(MotionEvent event);
public boolean dispatchGenericMotionEvent(MotionEvent event);
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event);
@Nullable
public View onCreatePanelView(int featureId);
public boolean onCreatePanelMenu(int featureId, Menu menu);
public boolean onPreparePanel(int featureId, View view, Menu menu);
public boolean onMenuOpened(int featureId, Menu menu);
public boolean onMenuItemSelected(int featureId, MenuItem item);
public void onWindowAttributesChanged(WindowManager.LayoutParams attrs);
public void onContentChanged();
public void onWindowFocusChanged(boolean hasFocus);
public void onAttachedToWindow();
public void onDetachedFromWindow();
public void onPanelClosed(int featureId, Menu menu);
public boolean onSearchRequested();
public boolean onSearchRequested(SearchEvent searchEvent);
@Nullable
public ActionMode onWindowStartingActionMode(ActionMode.Callback callback);
@Nullable
public ActionMode onWindowStartingActionMode(ActionMode.Callback callback, int type);
public void onActionModeStarted(ActionMode mode);
public void onActionModeFinished(ActionMode mode);
default public void onProvideKeyboardShortcuts(
List<KeyboardShortcutGroup> data, @Nullable Menu menu, int deviceId) { };
default public void onPointerCaptureChanged(boolean hasCapture) { };
}是不是看到了熟悉的dispatchTouchEvent dispatchKeyEvent……方法
Activity.java 实现了Window.Callback接口，这样当这个PhoneWindow对象接收到系统给它分发的IO输入事件，例如，键盘和触摸屏事件，转发给与它所关联的Activity组件处理
Window.setWindowControllerCallback
这个接口也是Window.java里，activity实现了WindowControllerCallback
/** @hide */
public interface WindowControllerCallback {
/**
* Moves the activity from
* {@link android.app.ActivityManager.StackId#FREEFORM_WORKSPACE_STACK_ID} to
* {@link android.app.ActivityManager.StackId#FULLSCREEN_WORKSPACE_STACK_ID} stack.
*/
void exitFreeformMode() throws RemoteException;
/**
* Puts the activity in picture-in-picture mode if the activity supports.
* @see android.R.attr#supportsPictureInPicture
*/
void enterPictureInPictureModeIfPossible();
/** Returns the current stack Id for the window. */
int getWindowStackId() throws RemoteException;
/** Returns whether the window belongs to the task root. */
boolean isTaskRoot();
}从方法名儿可以看出，这个接口是为模式切换服务的，Freefor, PictureInPicture
Window.setOnWindowDismissedCallback
窗口消失的回调窗口
/** @hide */
public final void setOnWindowDismissedCallback(OnWindowDismissedCallback dcb) {
mOnWindowDismissedCallback = dcb;
}
/** @hide */
public interface OnWindowDismissedCallback {
/**
* Called when a window is dismissed. This informs the callback that the
* window is gone, and it should finish itself.
* @param finishTask True if the task should also be finished.
* @param suppressWindowTransition True if the resulting exit and enter window transition
* animations should be suppressed.
*/
void onWindowDismissed(boolean finishTask, boolean suppressWindowTransition);
}
Window.setSoftInputMode
public abstract class Window {
......
private boolean mHasSoftInputMode = false;
......
public void setSoftInputMode(int mode) {
final WindowManager.LayoutParams attrs = getAttributes();
if (mode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
attrs.softInputMode = mode;
mHasSoftInputMode = true;
} else {
mHasSoftInputMode = false;
}
dispatchWindowAttributesChanged(attrs);
}
......
}
当参数mode的值不等于SOFT_INPUT_STATE_UNSPECIFIED时，就表示当前窗口被指定软键盘输入区域的显示模式，这时候Window类的成员函数setSoftInputMode就会将成员变量mHasSoftInputMode的值设置为true，并且将这个显示模式保存在用来描述窗口布局属性的一个WindowManager.LayoutParams对象的成员变量softInputMode中，否则的话，就会将成员变量mHasSoftInputMode的值设置为false
设置完成窗口的软键盘输入区域的显示模式之后，调用dispatchWindowAttributesChanged()
/**
* {@hide}
*/
protected void dispatchWindowAttributesChanged(WindowManager.LayoutParams attrs) {
if (mCallback != null) {
mCallback.onWindowAttributesChanged(attrs);
}
}通过onWindowAttributesChanged通知activity窗口发生了变化
Window.setWindowManager
public void setWindowManager(WindowManager wm, IBinder appToken, String appName) {
setWindowManager(wm, appToken, appName, false);
}
/**
* Set the window manager for use by this Window to, for example,
* display panels. This is <em>not</em> used for displaying the
* Window itself -- that must be done by the client.
*
* @param wm The window manager for adding new windows.
*/
public void setWindowManager(WindowManager wm, IBinder appToken, String appName,
boolean hardwareAccelerated) {
mAppToken = appToken;
mAppName = appName;
mHardwareAccelerated = hardwareAccelerated
|| SystemProperties.getBoolean(PROPERTY_HARDWARE_UI, false);
if (wm == null) {
wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);
}
mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);
}参数appToken用来描述当前正在处理的窗口是与哪一个Activity组件关联的，它是一个Binder代理对象，引用了在ActivityManagerService这一侧所创建的一个类型为ActivityRecord的Binder本地对象,在前面Android AMS(一) App启动过程之Task,进程创建流程讲到,每一个启动起来了的Activity组件在ActivityManagerService这一侧，都有一个对应的ActivityRecord对象，用来描述该Activity组件的运行状态。这个Binder代理对象会被保存在Window类的成员变量mAppToken中，这样当前正在处理的窗口就可以知道与它所关联的Activity组件是什么。
参数appName用来描述当前正在处理的窗口所关联的Activity组件的名称，这个名称会被保存在Window类的成员变量mAppName中。
最后得到mWindowManager用来维护当前正在处理的应用程序窗口。
至此，我们就分析完成一个Activity组件所关联的应用程序窗口对象的创建过程了。从分析的过程可以知道：
1. 一个Activity组件所关联的应用程序窗口对象的类型为PhoneWindow。
2. 这个类型为PhoneWindow的应用程序窗口是通过一个类型为WindowManagerImpl的本地窗口管理器来维护的。
3. 这个类型为PhoneWindow的应用程序窗口内部有一个类型为DecorView的视图对象，这个视图对象才是真正用来描述一个Activity组件的UI的。
